Structural Analysis of Ernst Tinaja Canyon Focusing on Strike-Slip Faulting and Folding, Big Bend National Park, Texas

<p>Basement and cover rocks in the Sierra Del Carmen Mountains in eastern Big Bend National Park were affected by multiple tectonic events. The Big Bend/Trans-Pecos area experienced shearing during Precambrian formation of the Texas Lineament, compression during the Paleozoic Ouachita-Marathon Orogeny and the Cretaceous-early Tertiary Laramide Orogeny, Tertiary volcanism, and Basin and Range extension. The study area is in Big Bend National Park on the western slopes of the Sierra Del Carmen range at Ernst Tinaja, an erosional pothole in the Cretaceous Buda Limestone. The pothole is in a narrow slot canyon that also features intense folds in thin, flaggy strata of the overlying Boquillas Formation. The complex geology of the Sierra Del Carmen region has been regionally mapped but is lacking in published detailed geologic maps, making this an interesting location for geologic reinvestigation focused on the structural geology of the area. This study presents field data for numerous structures in the study area including folds, normal and thrust faults and a previously unmapped, large dextral strike-slip fault, with associated negative flower structure. Theories for the mechanisms and kinematics of deformation are discussed and a model is presented for the overall tectonic history of the area based on field evidence. Orientations of faults, folds, slickenlines, chatter marks, and fault-juxtapositions of formations were measured. Normal fault mean trends were found to be N16°W, 63°SW and NE, thrust faults mean trends were found to have a mean trend of N19°W, 45°SW. Strike-slip faults mean trends in the study area are N9°W, 70°SW and NE. ii Fold axial planes in the study area have a mean strike and dip of N13°W, 71°NE and SW, and bedding in the study area is consistent and trends N25°W, 24°SW. Prominent horizontal slickenlines support the interpretation of strike-slip fault in the N-S trending portion of Ernst Canyon. Three interpretations of the structural evolution of the study area were developed. The first interpretation is that right-lateral movement indicators in the N-S trending canyon were created by dextral strike-slip movement associated with the Basin and Range. This movement reactivated Laramide sinistral strike-slip fault. The second interpretation states the N-S canyon is part of a relay ramp, connecting two en-echelon Basin and Range normal faults. The third interpretation is a combination of the first and second interpretations, and theories that a sinistral strike-slip fault was created during the Laramide Orogeny, Basin and Range normal faults and relay ramps developed next and a late pulse of strike-slip movement during the Basin and Range reactivated the Laramide sinistral strike-slip fault, but with a dextral shear sense.</p>

Name thesis:degree_name

Master of Science - Geology

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Geology

Year dc:date.available

2017

Author dc:creator

• Silberstorf, Ryan Robert

Contributors dc:contributor

• Dr. Chris Barker
• Dr. R. LaRell Nielson
• Dr. Kevin Stafford

• geology
• structural geology
• Big Bend National Park
• Ernst Tinaja
• strike-slip fault
• relay ramp

Repository record dc:identifier

https://scholarworks.sfasu.edu/etds/89

OAI identifier oai:identifier

oai:scholarworks.sfasu.edu:etds-1093